A systematic investigation of the disposition of acetylmethadol in rat, baboon and man is designed to provide comparative information on the rates, pathways and routes of elimination in these three species. Plasma time course, urinary and fecal excretion rates will be determined following acute and chronic administration to rats and baboons. The baboon will provide a model for a study of the role of the biliary system in the disposition of acetylmethadol. In rat particular emphasis will be directed toward the identification of persistent metabolites in brain and liver tissue. Plasma and urine samples will be provided by acetylmethadol maintenance patients. Methods used in these studies will include radioisotope-labeling, gas-liquid chromatography, high pressure liquid chromatography and mass spectrometry. These methods together with solvent extraction, thin-layer and column chromatography will provide qualitative and quantitative information on the disposition of acetylmethadol in these species.